The present invention relates generally to chucks for use with drills or with electric or pneumatic power drivers. More particularly, the present invention relates to a chuck of the keyless type which may be tightened or loosened by hand or by actuation of the driver motor.
Both hand and electric or pneumatic tool drivers are well-known. Although twist drills are the most common tools used with such drivers, the tools may also comprise screwdrivers, nut drivers, burrs, mounted grinding stones, and other cutting or abrading tools. Since the tools may have shanks of varying diameter or may have a polygonal cross-section, the device is usually provided with a chuck that is adjustable over a relatively wide range. The chuck may be attached to the driver by a threaded or tapered bore.
A wide variety of chucks have been developed in the art. In one form of chuck, three jaws spaced circumferentially approximately 120xc2x0 apart from each other are constrained by angularly disposed passageways in a body attached to the driveshaft. The chuck is configured so that rotation of the body in one direction with respect to a constrained nut forces the jaws into or away from gripping relationship with a tool shank. Such a chuck may be keyless if it can be tightened or loosened by manual rotation. Examples of such chucks are disclosed in U.S. Pat. Nos. 5,125,673 and 5,193,824, commonly assigned to the present assignee and the entire disclosures of which are incorporated by reference herein. Various configurations of keyless chucks are known in the art and are desirable for a variety of applications.
FIG. 2 illustrates, in cross-section, a typical chuck jaw construction in which each of three jaws 200 includes a back surface 202 and an opposing tool-engaging surface formed by a ridge 204 disposed generally parallel to the chuck axis. Two generally planar side surfaces 206 extend from ridge 204 to the back surface. The side surfaces on each jaw 200 define a 120xc2x0 angle xcex4 extending through the jaw. Thus, each side surface on a jaw 200 is parallel to a side surface of an adjacent jaw. When the chuck is moved to its fully closed position as shown in FIG. 2, the jaw side surfaces abut each other.
Other tool-engaging surfaces are known. For example, the tool-engaging surface may be formed by an inner ridge parallel to the chuck axis and two outer ridges parallel to the inner ridge. A pair of respective troughs sit between the inner ridge and the outer ridges so that the jaw""s cross-section is in the shape of a W. Generally, side surfaces that extend from the outer ridges to the jaw""s back surface define a 120xc2x0 angle between them through the jaw so that each side surface is parallel to the side surface of its adjacent jaw.
The present invention recognizes and addresses disadvantages of prior art construction and methods.
Accordingly, it is an object of the present invention to provide an improved chuck for use with a powered driver.
This and other objects are achieved by a chuck for use with a manual or powered driver having a rotatable drive shaft. The chuck includes a generally cylindrical body having a nose section and a tail section. The tail section is configured to rotate with the drive shaft. The nose section has an axial bore formed therein. A plurality of jaws are moveably disposed with respect to the body to and away from the axial bore. A generally cylindrical sleeve is in driving communication with the jaws so that rotation of the sleeve with respect to the body in a closing direction moves the jaws toward the chuck axis and so that rotation of the sleeve with respect to the body in an opening direction moves the jaws away from the chuck axis. The chuck includes a first set of interengaged threads by which the sleeve engages one of the body and the jaws so that relative rotation between the first threads drives the jaws toward or away from the chuck axis. The chuck includes a second set of interengaged threads by which the sleeve engages one of the body and the jaws so that relative rotation between the second threads drives the jaws toward or away from the chuck axis. The first thread set defines a first pitch so that when the jaws close, the first threads rotationally lock in the closing direction. The second thread set defines a second pitch that is higher than the first pitch so that when the jaws close, the second threads are relatively rotatable in the closing direction.